In particular, let \(\mathcal {T}_{j,i}\)  be the time interval between sending two consecutive sub-vectors, \(\hat{x}_{i}\)  and \(\hat{x}_{i+1}\) , to the worker node \(j\)  from the master node. As illustrated in Fig. REF , in order to maximally reduce the computation delay, the desired \(\mathcal {T}_{j,i}\)  will minimize the idle time at the worker node \(j\)  while not overloading it. That is, ideally, the worker node \(j\)  should receive \(\hat{x}_{i+1}\)  immediately after it completes the previous task, i.e., computing \(a * \hat{x}_{i}\) . To determine \(\mathcal {T}_{j,i}\) , the key is thus to estimate the time required for the master node to compute \(a * \hat{x}_{i}\) , denoted as \(T^{comp}_{j,i}\) . Here, we apply the method introduced in [1]} to estimate the expected time required for the worker node \(j\)  to compute \(a * \hat{x}_{i}\) . In particular, the expected computation time \(\mathbb {E}[T^{comp}_{j,i}]\)  can be estimated by following equations:
\(\mathbb {E}[T^{comp}_{j,i}] \approx \frac{t_{j,i}^{c} - t_{j,i}^{u}}{c_j} \) 
\(t_{j,i}^{c} \approx t_{j,i}^{r} - \frac{B_r}{B_r + B_x}RTT_j\) 
\(t_{j,i}^{u} \approx t_{j,i-1}^{u} + \max (0, RTT_j - t_{j,i-1}^{r} - t_{j,i}^{s})\) 
